This invention relates to aeronautics and more specifically to airfoils, of the so called biplane type, and their relationship and arrangement with respect to one another as distinguished from airfoil construction.
The design of an aircraft, particularly commercial and corporate types, which can safely operate in limited areas, such as city centers and suburban airports, has been and still is a goal of the aircraft industry. In this endeavor the industry has leaned towards a VTOL, vertical take off and landing, and STOL, short take off and landing, aircraft. The complexity of the VTOL type of aircraft together with its marginal safety and performance in certain flight areas, as well as its high cost, has resulted in directing the efforts of some manufacturers towards the STOL concept.
In the majority of instances a VTOL aircraft utilizes a rotary wing or a tilt-jet flow principle for propulsion, such as in the British Harrier type of aircraft. As distinguished from the foregoing a STOL aircraft employs lower wing and power loadings plus high lift devices, such as large slots and flaps to increase the lift characteristics of the aircraft and thus provide various degrees of STOL capability.
It is known that aspect ratio serves an important function in aircraft wing design. A high performance glider is made with a very high aspect ratio while a high aspect ratio is employed in high load cargo or passenger planes. The high aspect ratio provides less induced drag and a higher lift at a lower angle of attack while increasing the range of the aircraft. On the other hand the same type of aircraft having a very low aspect ratio wing would be relatively inefficient.
A very low aspect ratio wing of proper design gives high lift and drag at large landing angles. However its drag is low at low angles of attack as is its lift. A low aspect ratio wing is less efficient than a high aspect ratio wing for high load long range duties, but a low aspect ratio wing is very good for steep approach landings while its stall angle of attack is very high. Thus each type has its advantages and its disadvantages.